Should I specify to show the reader a summary or full text of an article?

There are only two factors you need to consider in this case... the first is the length of the posting and the second is the number of articles. It's important to know that the size of an RSS feed will be a factor, especially as the file has to be re-downloaded each time it's syndicated with (and this can use a serious amount of bandwidth if you have queries to it every 5 minutes or so). If however your posts are of a relative size and your syndication feed doesn't end up in the 500KB style size, you should always attempt to give the full posting. The only people who argue about it resulting in less visits to their website are simply misinformed and basing that judgement upon erroneous information. The whole point of an RSS feed is NOT to tell people that something new has been posted (Twitter exists for that), but to deliver fresh content to your end-users so that they can consume it using a client or method which they feel comfortable (like if you send an email). The aim of any RSS feed IS to eliminate the need to keep visiting your website as the loyalty will be struck by their ability to save time and get the info as they wish, trying to bait them with advertisements of new content contradicts the purpose of syndication and it's outright insulting to the people who show their loyalty.

I say full feed. It's good to leave it to your site visitors to decide how they want to be informed. If they'd rather read your articles via the feed, then that should be their prerogative.

Users should decide how they access information and we, as designers, developers, bloggers, etc., have the ability to give them exactly that; as much control over how they obtain information as possible.

It depends on a whole lot of factors. I have known of people who don't like a full because it results in fewer people actually visiting their site and others who don't like using too terse a summary for exactly the same reason.

Perhaps you should try out different alternatives so as to find out which gives the best result for your particular circumstances.

Thanks for your response - That's my mindset aswell it's a bit of a catch 22 - hmm I am going with the summaries for now but I would be really interested to hear from any other experienced bloggers and what feedback they have had from their readers - if anyone would like to share their experience/preferences it would be greatly welcomed, thank you!

Thanks Maleika! I've just literally had this chat with my brother a few moments ago and he said the exact same thing - particularly for those who subscribe via email - they don't want to visit the site, they would rather just read the articles from the comfort of their email client etc... so yes my priority is to keep the readers happy so I will go with full text, thank you for your response!